Unbalanced to balanced line transformer



May 2 7, 1952 P. D. COLEMAN UNBALANCED To BALANCED LINE TRANSFORMER Filed Jan. 5, 1945 AVA ' ro mwfcrae- F|G.4 By

Patented May 27, 1952 f 'I UNBALAN CED TO BALAN CED LINE TRANSFORMER` 1 Paul D. Coleman, Dayton, Ohio, assignorto The United States of America as represented by the Secretary of War Application January 3, 1945, Serial No. 571,191

(Granted under Vthe act ol March 3, 1883, as

Claims.

amended April 30, 1928; 370 O. G. 757) The invention described herein may be manufactured and used by or for the Goverment for governmental purposes, without the payment to me of any royalty thereon.

The invention to be hereinafter described relates to transformers and more particularly to transformers for making a transformation from a 50 ohm unbalanced line to a 100 ohm balanced line.

Among the main objects of the present invention are to overcome the disadvantages of the excessively large and weighty prior art transformers as well as other disadvantages, and produce a simple, emcient, light weight, compact transformer of the type stated which may be quickly made from readily obtainable materials. with relatively few operations and corresponding comparatively low cost.

In order to more clearly disclose the construction, operation and use of the invention, reference Fig. 2 is an enlarged cross section of one coaxial cable;

Fig. 3 is a like view of the combined cable, referred to as composite;

Fig. 4 is an enlarged, longitudinal cross section,

diagrammatically, of the connections between cables.

The unbalancedv line is of 50 ohm coaxial cable, while the balanced line consists of two 50 ohm coaxial cables.

The invention comprises a special coaxial cable specially combined to provide another special cable which I refer to or call a composite cable, being elements of two such coaxial cables combined into one cable.

The coaxial cable, shown in enlarged cross section in Figure 2, comprises the center conductor I, dielectric 2, conducting enclosing or inner braid 3, dielectric layer 4 and the outer braid or conductor 5. By providing the outer conducting braid 5 which is absent from the usual coaxial cable, the coaxial cable of this invention is, actually, a cable within a cable, i. e. conductors I and 3 may be connected, or conductors 3 and 5 may be connected.

Two of these special coaxial cables are then combined to provide the composite cable of this f invention, shown in cross section in Figure 3. In so combining the two cables,- the 4outer braid conductor 5 of each is removed throughout the length Yto be combined. They are laid parallel with the dielectrics 4 contacting. -I n this position'a conductor braid 6 is woven orl otherwise wrapped about the assembled coaxial cables. This assemblage is vapproximately elliptical in lateral cross section, the short axishaving a length sub stantially that of the diameter of thecomponent coaxial cable while the long axis is of substantially twice that length. This assemblage, as will be clear on reference to Fig. 3 comprises ve con-y ductors, i.Y e. outer conductor 6, the two inner braid conductors 3 and the tors I.

Reference is now made to Fig. 4. In Fig. 4, the left-hand composite cable is designated A, A', while the pair of coaxial cables on the right-hand is designated B, B'. This view shows the total length, in cross-section, of the combined cables between connectors 9 and I0, the center of this view being -the point where clip I I of Fig. l is applied. Terminal 9 of Fig. 1 is connected to the left-hand end of the unbalanced 50 ohm cable line formed by the center conductor I and the inner braid 3 of coaxial cable A of the composite cable A, A'. thereof and soldered to the inner braid 3 of cable A. Thereafter, the connection of A to A may be tracedV through a line that is one-quarter of a wavelength at the mean operating frequency range, and is formed by conductors I and 3 of cable A, as indicated. The center conductor I two center conduc of the coaxial cable A is deflected near the center of Fig. 4, cut, and soldered to the inner braid conductor 3 of coaxial cable A. Inner braid 3 of cable A continues as the inner braid 3 of c0- axial cable B. 'Ihe inner braid 3 of coaxial cable A is connected to the inner braid 3 of coaxial cable B. Cables B and B are respectively connected to connectors I0 of Fig. 1. Thus, the inner braid conductors 3 of coaxial sections B and B' become the center conductors of a 100 ohm balanced line, the outer conductors being the outer braids 5. These coaxial sections B and B are, as indicated, of the same electrical length as the special composite cable hereinabove described. In Fig. 4, conductors 5 and 6 are shown as being grounded. These conductors are actually grounded near their centers through the clip II, shown in Fig. 1.

These special, flexibler coaxial cables combined as described into the special composite cable of this invention, as a unit, are coiled and mounted Cable A' is shorted at the left end as shown in Fig. 1: So mounted, the assemblage constitutes a complete transformer unit readily enclosed within a suitable protecting housing or case l.

The mounting plate or base 8 may be made in any suitable and well known manner, as by stamping, for instance. with the input connector 9 for the unbalanced end of the line and a pair of connectors I for the balanced ends, all as will be readily understood. Preferably, base 8 is provided with short flanges which act as guides to facilitate inserting the unit into its case and withdrawing it from its case. Preferably a suitable clip I I is provided at about longitudinal center of the plate and adapted to extend across or bridge the cable, in coiled form.

The cables may be held in coiled form either by wrapping with cord, tape, or the like or by using one or more readily applied clips.

The flexibility of this type of cable permits ready compact coiling and by arranging the component coaxial coils as stated the short diameter of the ellipse of that composite portion is approximately aligned with the diameter of the coil. This approximately maintains the same flexibility in the composite portion as exists in the separate coaxial sections. Cables so made and assembled may be quickly, easily and compactly coiled.

As will appear on reference to Fig. 4 the center conductor I of the component coaxial cable A and of cableV B is unused or idle, throughout. These components could be made without it. However, it is simpler to make all components the same and leave that conductor unused than it is to make one set of coaxial cables with a center conductor and another set without. From the same view, it will also be obvious that the center conductor I of terminal section B is dead or idle because it has been cut near the point of deflection of conductor I of cable A where it is soldered to the inner braid conductor 3 of the component A. Thus cable A of the two components A and B must have a central conductor I whereas the remaining one need not have a central conductor.

It is thought that the construction, operation and use of the invention will be clear from the preceding detailed description.

Having thus described my invention what I claim and desire to protect by Letters Patentnis:

1. An unbalanced to balanced line transformer, comprising a composite unbalanced cable including first and second flexible parallel cables each It is, of course, provided y having a center and a separate enclosing cuter conductor, said cables being compositely enclosed in an outer conductor of approximately onequarter of a wavelength, one end of said second cable being shorted at one end of said composite conductor to the separate outer conductor 0f said rst cable, and the center conductor of said first cable being shorted to the separate outer conductor of said second cable at the other end of said composite conductor, and third and fourth flexible balanced cables, each having center, inner, and outer conductors of approximately onequarter of a wavelength, the inner conductors of said third and fourth cables being respectively connected at one end to the separate outer conductors of said rst and second cables at the other end of said composite conductor, and the center conductor at said one end 0f said fourth cable being connected to the center conductor of said second cable at the other end thereof, said cables being arranged to form a coil, said one end of said rst cable being adapted to receive an unbalanced input and the other ends of said third and fourth cables being adapted to provide the balanced output therefrom.

2. The transformer of claim l, further including means for maintaining said cables in the form of a coil.

3. The transformer of claim 2, wherein said means comprises clip means connected to the other ends of said rst and second cables, and to the one ends of said third and fourth cables.

4. The transformer of claim 1, further including a housing for said cables, said housing having an unbalanced input connector coupled to the one end Vof said first cable and two balanced output connectors, each respectively coupled to the other Yends of said third and fourth cables.

5. The transformer of claim 4, further including clip means connected to the other ends of said rst and second cables and to the one ends of said third and fourth cables, for maintaining said cables in coil form.

PAUL D. COLEMAN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENT 

